The value space of an attribute or element that contains time span content is closely related to duration content as described in ISO 8601. When creating an attribute or element that contains time span content, the attribute or element values are formatted per the W3C specification. Please see the W3C specification for more details.

Behavior is lax when casting to a Nullable<T> of TimeSpan from an attribute or element. Even if the attribute or element value is not formatted exactly per the W3C specification, the value is appropriately converted to a Nullable<T> of TimeSpan.